A bipartisan group of eight senators unveiled a new immigration reform proposal Monday that would allow most of the estimated 11 million illegal immigrants currently living in the country to eventually become citizens.

The senators unveiled details of the proposal during a press conference Monday afternoon, calling it a "tough but fair" way to reform the nation's immigration system for the first time since 1986, when President Ronald Reagan signed into law a bill that legalized nearly 3 million immigrants.

"We still have a long way to go, but this bipartisan blueprint is a major breakthrough," said New York Democratic Sen. Chuck Schumer, who added that they plan to have a bill officially introduced by March and passed through the Senate by "late spring or summer."

The senators, who have been meeting about the issue behind closed doors since December, include Republicans John McCain of Arizona, Marco Rubio of Florida, Jeff Flake of Arizona and Lindsey Graham of South Carolina, and Democrats Michael Bennet of Colorado, Dick Durbin of Illinois, Robert Menendez of New Jersey and Schumer.

Since the presidential election, in which more than 70 percent of Hispanic voters supported President Barack Obama's re-election, the appetite in Washington for comprehensive immigration reform has increased for both parties. The senators behind the effort believe they have a window of opportunity to pass a bill, even though similar efforts failed many times in the past.

"For the first time ever, there's more political risk in opposing immigration reform than supporting it," Schumer said at the press conference. "We believe we have a window of opportunity to act."

McCain, who led the Republican side of failed bipartisan reform efforts in 2006, pointed to Republican fear of losing Hispanic support as a source of hope to secure passage of the bill. "The Republican Party is losing the support of our Hispanic citizens," McCain said.

It still remains to be seen whether the senators' blueprint will clash with Obama's vision for reform, which he will announce Tuesday in more detail in an appearance in Las Vegas. The senators' path to citizenship for illegal immigrants is less direct and could take longer than what Obama has outlined in the past.

When asked why they unveiled their blueprint before the president's speech, the senators said they informed Obama over the weekend that they had reached an agreement. "We don't have much time. We came to an agreement this weekend and we wanted to move quickly," Schumer said. "It seems to me that the Senate is the most fortuitous place to move forward first."

The senators' plan puts forward several hurdles before undocumented immigrants could obtain permanent residence visas, called green cards, which is the first step towards citizenship.

First, immigrants would apply for temporary legal status by registering with the government, completing a background check and paying a fine. Before any immigrant could obtain a green card, "a commission comprised of governors, attorneys general, and community leaders living along the Southwest border" must recommend that the government has taken enough steps to beef up border security and has also implemented a system that tracks when temporary visitors have left the country. It's unclear how long that would take, especially since border state governors are divided on how secure the border is now and ideally should be in the future.

The plan also says that no undocumented immigrant would receive a green card until every legal immigrant who is currently waiting for a green card has already received it. Wait times for green cards can be as long as 20 years in extreme cases, depending on whether the applicant is being sponsored by an employer or a family member. Family-based immigration, especially when a U.S. citizen is attempting to sponsor his or her sibling, can have especially long wait times.

The blueprint says the senators want to reduce these wait times and drastically increase legal, high-skilled immigration, so it's possible that the bill could expedite the process. If not, illegal immigrants seeking a green card could be waiting for decades.

The plan also excludes the children of illegal immigrants, commonly referred to as "Dreamers," as well as agricultural workers from the long wait for a green card. To prevent future illegal immigration, the blueprint also calls for a mandatory employment verification system.

Obama's blueprint asks for a wait time of eight years before illegal immigrants could get green cards, during which time they could live and work legally in the country. After five years with a green card, immigrants could apply to become citizens.

Speaking on the Senate floor before the announcement, Majority Leader Harry Reid praised members of the committee for proposing an outline for an immigration overhaul and said he would do "everything" in his power to ensure an immigration bill passes through the upper chamber.

"Nothing short of bipartisan success is acceptable to me," Reid, a Democrat from Nevada, said. "There is no reason why we should not pass comprehensive immigration reform immediately."

Immigration advocates, who generally favor a fast path to citizenship for the country's illegal immigrants, mostly praised the senators for adding to the "momentum" of reform, but did not comment on the specifics of the plan.

"Creating a 21st century immigration process won't be easy, but the framework the senators are proposing is a powerful and practical start to the legislative process, and it will make the peaks and valleys ahead much easier to traverse," said Ali Noorani, executive director of the the National Immigration Forum, in a statement.

But Chris Rickerd, policy counsel at the American Civil Liberties Union, said his organization has "concerns" that the lengthy time frame and fine might discourage people from applying to legalize. Rickerd also noted that some people might be excluded from legalization because they were prosecuted for immigration-related crimes in their states. For example in Arizona, illegal immigrants can be charged with "self smuggling," which is a felony that does not exist in other states.

Groups that favor less immigration, meanwhile, have blasted the plan as "amnesty."

"Like previous amnesty proposals, this most recent iteration creates a 'path to citizenship' for nearly all illegal aliens and offers empty promises of enforcement without providing any concrete details," said the Federation of American Immigration Reform in a statement.

The senators unveiling the blueprint conceded that there would be much work ahead transforming their outline of ideas into the law, but expressed optimism that, unlike past attempts, there would be enough will between both parties to pass a comprehensive bill.

"It won't be easy," Durbin said. "It will take them time and determination."